1. Field of the Invention
The present invention relates to a steering control system for a moving vehicle, and more particularly to a steering control system for the travel of a moving automobile, an unmanned mobile and carrying device in a factory, or an automated vehicle for use in agriculture, civil engineering machinery and the like along a traveling course comprising a straight traveling course and a turning course.
2. Description of the Prior Art
Heretofore, as a system for detecting a present position of a moving body such as the moving vehicles as described above, there has been proposed a system provided with a means for scanning a light beam emitted from a moving body in the circumferential direction or every azimuthal directions centering around the moving body, light-reflecting means for reflecting to return the light beam in the direction of incident light and secured at at least three positions apart from the moving body, and a beam receiver means for receiving light reflected from the light-reflecting means (Japanese Patent Laid-open No. 67476/1984).
In the above mentioned prior art, differential azimuthes between adjoining two of three light-reflecting means centering around the moving body are detected on the basis of the received beam output of the light-receiving means, and then a position of the moving body is operated based on the detected differential azimuthes and positional information of the light-reflecting means which have been previously set.
However, in the above described prior art, since a position of the moving body is detected on the basis of the output of the beam receiver means whereby a traveling direction of the moving body is controlled, when the moving body is rotated at a large angular velocity, there is a possibility of producing a significant error in the result of calculation for the position. Accordingly, there has been a problem that control for steering becomes difficult in a traveling state for such a course in which an orientation of the moving body is changed abruptly as in a turning course.
With respect to the above problem, if a turning speed of the moving body is slower significantly than a traveling speed thereof in a straight traveling course, there is not a fear of producing a remarkable error in the calculation of position. In this case, however, there arises another problem that a considerable period of time is required until turning of the moving body is completed so that working efficiency decreases.
As a countermeasure therefor, there has been proposed in Japanese Patent Laid-open No. 269610/1987 a control system constructed in such manner that a beam receiver means is composed of three independent beam receivers and in addition, a steering control means for straight traveling course and a steering control means for turning course are separately provided from one another, wherein the steering control means for the turning course is operated to perform a steering control on the basis of information for steering control which has been previously set and stored, and the reflected light beam to be detected by each of the three beam receivers is switched and changed at every time of starting as well as finishing a turn of the moving body, and then a position of the moving body in the following straight traveling course is calculated.
In the above conventional system, however, since three independent rotating beam receivers are provided, there have been such problems that the light receivers means becomes larger in size and more expensive and that the beam receivers corresponding to the respective light-reflecting means must be switched in every event of effecting turning motion of the moving body. Furthermore, there is a necessity of setting and storing steering positional information for a turning motion.